#include "stdio.h"
#include "stdlib.h"

#include "math.h"
#include "time.h"

#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0
#define MAXSIZE 20 /* 存储空间初始分配量 */

typedef int Status;

typedef int QElemType; /* QElemType类型根据实际情况而定，这里假设为int */

typedef struct QNode /* 结点结构 */
{
    QElemType data;
    struct QNode *next;
} QNode, *QueuePtr;

typedef struct /* 队列的链表结构 */
{
    QueuePtr front, rear; /* 队头、队尾指针 */
} LinkQueue;

Status visit(QElemType c)
{
    printf("%d ", c);
    return OK;
}

/* 构造一个空队列Q */
Status InitQueue(LinkQueue *Q)
{
    Q->front = Q->rear = (QueuePtr)malloc(sizeof(QNode));
    if (!Q->front)
        exit(OVERFLOW);
    Q->front->next = NULL;
    return OK;
}

/* 销毁队列Q */
Status DestroyQueue(LinkQueue *Q)
{
    while (Q->front)
    {
        Q->rear = Q->front->next;
        free(Q->front);
        Q->front = Q->rear;
    }
    return OK;
}

/* 将Q清为空队列 */
Status ClearQueue(LinkQueue *Q)
{
    QueuePtr p, q;
    Q->rear = Q->front;
    p = Q->front->next;
    Q->front->next = NULL;
    while (p)
    {
        q = p;
        p = p->next;
        free(q);
    }
    return OK;
}

/* 若Q为空队列,则返回TRUE,否则返回FALSE */
Status QueueEmpty(LinkQueue Q)
{
    if (Q.front == Q.rear)
        return TRUE;
    else
        return FALSE;
}

/* 求队列的长度 */
int QueueLength(LinkQueue Q)
{
    int i = 0;
    QueuePtr p;
    p = Q.front;
    while (Q.rear != p)
    {
        i++;
        p = p->next;
    }
    return i;
}

/* 若队列不空,则用e返回Q的队头元素,并返回OK,否则返回ERROR */
Status GetHead(LinkQueue Q, QElemType *e)
{
    QueuePtr p;
    if (Q.front == Q.rear)
        return ERROR;
    p = Q.front->next;
    *e = p->data;
    return OK;
}

/* 插入元素e为Q的新的队尾元素 */
Status EnQueue(LinkQueue *Q, QElemType e)
{
    QueuePtr s = (QueuePtr)malloc(sizeof(QNode));
    if (!s) /* 存储分配失败 */
        exit(OVERFLOW);
    s->data = e;
    s->next = NULL;
    Q->rear->next = s; /* 把拥有元素e的新结点s赋值给原队尾结点的后继，见图中① */
    Q->rear = s;       /* 把当前的s设置为队尾结点，rear指向s，见图中② */
    return OK;
}

/* 若队列不空,删除Q的队头元素,用e返回其值,并返回OK,否则返回ERROR */
Status DeQueue(LinkQueue *Q, QElemType *e)
{
    QueuePtr p;
    if (Q->front == Q->rear)
        return ERROR;
    p = Q->front->next;       /* 将欲删除的队头结点暂存给p，见图中① */
    *e = p->data;             /* 将欲删除的队头结点的值赋值给e */
    Q->front->next = p->next; /* 将原队头结点的后继p->next赋值给头结点后继，见图中② */
    if (Q->rear == p)         /* 若队头就是队尾，则删除后将rear指向头结点，见图中③ */
        Q->rear = Q->front;
    free(p);
    return OK;
}

/* 从队头到队尾依次对队列Q中每个元素输出 */
Status QueueTraverse(LinkQueue Q)
{
    QueuePtr p;
    p = Q.front->next;
    while (p)
    {
        visit(p->data);
        p = p->next;
    }
    printf("\n");
    return OK;
}

int main()
{
    int i;
    QElemType d;
    LinkQueue q;
    i = InitQueue(&q);
    if (i)
        printf("成功地构造了一个空队列!\n");
    printf("是否空队列？%d(1:空 0:否)  ", QueueEmpty(q));
    printf("队列的长度为%d\n", QueueLength(q));
    EnQueue(&q, -5);
    EnQueue(&q, 5);
    EnQueue(&q, 10);
    printf("插入3个元素(-5,5,10)后,队列的长度为%d\n", QueueLength(q));
    printf("是否空队列？%d(1:空 0:否)  ", QueueEmpty(q));
    printf("队列的元素依次为：");
    QueueTraverse(q);
    i = GetHead(q, &d);
    if (i == OK)
        printf("队头元素是：%d\n", d);
    DeQueue(&q, &d);
    printf("删除了队头元素%d\n", d);
    i = GetHead(q, &d);
    if (i == OK)
        printf("新的队头元素是：%d\n", d);
    ClearQueue(&q);
    printf("清空队列后,q.front=%u q.rear=%u q.front->next=%u\n", q.front, q.rear, q.front->next);
    DestroyQueue(&q);
    printf("销毁队列后,q.front=%u q.rear=%u\n", q.front, q.rear);

    return 0;
}
